The work refers to the relations between knowledge and psychic dynamism in two sermons preached in Brazil by Eusebio de Mattos and by Bento da Trindade. In such sermons, a conception of affective knowledge implying the activities of all animistic powers defines the ecstasy of the mystics as an act of the understanding applied to their supreme object, God. This vision is based on philosophic psychology and on the Aristotelic-Thomist theory of knowledge, used by the rhetoric of the Modern Age. Topics such as knowledge based on evidence and affective understanding introduce the conception of a participative modality of knowledge, which allows the change of nature in terms of transformation of the individual who knows into the known object.